Power efficiency improvement of an audio amplifier by adaptive control of a charge pump

ABSTRACT

A control circuit and method for an audio amplifier detect a signal for driving a speaker to control the switching frequency and the operation mode of a charge pump in the audio amplifier, to improve power efficiency of the audio amplifier. Preferably, a digital interface is further used to test the magnitude of the output signal of the audio amplifier, to reduce the costs of analog test. The charge pump has fewer switches and thus saves costs and die area of an integrated circuit. The control method needs only two phase control for the charge pump to generate a positive voltage and a negative voltage, and thus simplifies the operation of the circuit.

FIELD OF THE INVENTION

The present invention is related generally to a charge pump and acontrol method thereof and, more particularly, to a charge pump and amethod thereof for an audio amplifier.

BACKGROUND OF THE INVENTION

Audio amplifiers are used in audio output apparatus for drivingspeakers, for example, disclosed by U.S. Pat. Nos. 7,714,660 and7,701,294 and U.S. Pat. Publication No. 2011/0123048. FIG. 1 shows aconventional two channel audio amplifier for driving speakers 16 and 18,which includes amplifying circuits 10 and 13, power stages 12 and 14, again setting circuit 20 and a dual mode charge pump 22. The amplifyingcircuit 10 and power stage 12 establish a right channel audio amplifierfor generating an output signal SOR responsive to an input audio signalSa1 to drive the speaker 16, and the amplifying circuit 13 and the powerstage 14 establish a left channel audio amplifier for generating anoutput signal SOL responsive to an input audio signal Sa3 to drive thespeaker 18. Each of the speakers 16 and 18 may be a loudspeaker or anearphone.

An operational amplifier 32 and variable resistors 24, 26, 28 and 30establish the amplifying circuit 10 for generating differential signalsSa2P and Sa2N responsive to the audio signal Sa1. The variable resistors24 and 26 are connected to a first input terminal and a second inputterminal of the operational amplifier 32, respectively, the variableresistor 28 is connected between the first input terminal and a firstoutput terminal of the operational amplifier 32, and the variableresistor 30 is connected between the second input terminal and a secondoutput terminal of the operational amplifier 32. The power stage 12,which includes an operational amplifier 42 and variable resistors 34,36, 38 and 40, generates the output signal SOR responsive to thedifferential signals Sa2P and Sa2N to drive the speaker 16. The variableresistor 34 is connected between the first output terminal of theoperational amplifier 32 and a first input terminal of the operationalamplifier 42, the variable resistor 36 is connected between the secondoutput terminal of the operational amplifier 32 and a second inputterminal of the operational amplifier 42, the variable resistor 38 isconnected between the first input terminal and an output terminal of theoperational amplifier 42, and the variable resistor 40 is connectedbetween the second input terminal and a ground terminal of theoperational amplifier 42.

An operational amplifier 51 and variable resistors 43, 45, 47 and 49establish the amplifying circuit 13 for generating differential signalsSa4P and Sa4N responsive to the audio signal Sa3. The variable resistors43 and 45 are connected to a first input terminal and a second inputterminal of the operational amplifier 51, respectively, the variableresistor 47 is connected between the first input terminal and a firstoutput terminal of the operational amplifier 51, and the variableresistor 49 is connected between the second input terminal and a secondoutput terminal of the operational amplifier 51. The power stage 14,which includes an operational amplifier 52 and variable resistors 44,46, 48 and 50, generates the output signal SOL responsive to thedifferential signals Sa4P and Sa4N to drive the speaker 18. The variableresistor 44 is connected between the first output terminal of theoperational amplifier 51 and a first input terminal of the operationalamplifier 52, the variable resistor 46 is connected between the secondoutput terminal of the operational amplifier 51 and a second inputterminal of the operational amplifier 52, the variable resistor 48 isconnected between the first input terminal and an output terminal of theoperational amplifier 52, and the variable resistor 50 is connectedbetween the second input terminal and a ground terminal of theoperational amplifier 52.

The gain setting circuit 20 provides setting signals G1, G2, G3 and G4for controlling the variable resistors 24, 26, 28, 30, 34, 36, 38, 40,43, 44, 45, 46, 47, 48, 49 and 50, to thereby control gains of theamplifying circuit 10 and 13 and the power stages 12 and 14, and thusdetermines the overall gain of the audio amplifier. In addition, thegain setting circuit 20 determines a gain information Gset according tothe overall gain for the dual mode charge pump 22, to control theoperation mode of the dual mode charge pump 22. The dual mode chargepump 22 converts an input voltage Vin into a positive voltage Vp and anegative voltage Vn for the audio amplifier. When the dual mode chargepump 22 is in its first mode, Vp=+Vin and Vn=−Vin, and when the dualmode charge pump 22 is in its second mode, Vp=+Vin/2 and Vn=−Vin/2.

Power efficiency is an important parameter that dominates the powerconsumption of an audio amplifier, especially for a battery poweredsystem. This power efficiency refers to the ratio between the powersupplied to the speakers 16 and 18 and the power supplied by the dualmode charge pump 22. As shown in FIG. 1, in the condition that theoperation mode of the dual mode charge pump 22 remains unchanged, if theamplitudes of the output signals SOR and SOL reduce, the powerefficiency deteriorates. FIG. 2 shows waveforms of the positive voltageVp, the negative voltage Vn and the output signal SOR when the dual modecharge pump 22 operates in its second mode. At time t1, the outputsignal SOR has relatively large amplitude, so the difference ΔV1 betweenthe positive half-wave of the output signal SOR and the positive voltageVp is relatively small, thereby having a better power efficiency. Attime t2, the amplitude of the output signal SOR reduces, so thedifference ΔV2 between the positive half-wave of the output signal SORand the positive voltage Vp becomes larger, thereby having a poorerpower efficiency. Moreover, the conventional audio amplifier requiresexternal automatic test equipment (ATE) for testing whether the audioloop transition is correct, and thus requires higher test costs.

Charge pumps are well known circuits. For example, as disclosed by U.S.Pat. Publication No. 2011/0234305, FIG. 3 is a dual mode charge pump 22which includes a flying capacitor Cf1 connected between bonding pads 56and 58, a second flying capacitor Cf2 connected between bonding pads 60and 62, an input terminal 64 receiving an input voltage Vin, outputterminals 66 and 68 connected to output capacitors Co1 and Co2,respectively, a switch SW1 connected between the input terminal 64 andthe bonding pad 56, a switch SW2 connected between the bonding pad 56and the output terminal 66, a switch SW3 connected between the bondingpads 56 and 60, a switch SW4 connected between the bonding pad 58 and aground terminal GND, a switch SW5 connected between the bonding pads 58and 60, a switch SW6 connected between the bonding pads 58 and 62, aswitch SW7 connected between the bonding pad 62 and the ground terminalGND, a switch SW8 connected between the bonding pad 62 and the outputterminal 68, and a clock generator 54 providing signals CS1, CS2, CS3,CS4, CS5, CS6, CS7 and CS8 according to a gain information Gset forcontrolling the switches SW1, SW2, SW3, SW4, SW5, SW6, SW7 and SW8,respectively. As shown in FIG. 3, the conventional dual mode charge pump22 requires four bonding pads 56, 58, 60 and 62 for connection with twoflying capacitors Cf1 and Cf2, causing higher packaging costs of anintegrated circuit. Additionally, the dual mode charge pump 22 requiringtwo flying capacitors Cf1 and Cf2 needs eight switches SW1-SW8, makingthe costs and die area of the integrated circuit increased. Moreover,the conventional dual mode charge pump 22 can only provide the positivevoltage Vp of either +Vin or +Vin/2 and the negative voltage Vn ofeither −Vin or −Vin/2, without capability of arbitrarily adjusting thepositive voltage Vp or the negative voltage Vn.

FIG. 4 is a timing diagram of the signals CS1, CS2, CS3, CS4, CS5, CS6,CS7 and CS8 when the dual mode charge pump 22 of FIG. 3 provides thepositive voltage Vp of +Vin2 and the negative voltage Vn of −Vin2. Ascan be seen in FIG. 4, the conventional dual mode charge pump 22requires a three phase control to generate Vp=+Vin2 and Vn=−Vin2,causing its operation more complex.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a control circuitand a method for improving power efficiency of an audio amplifier.

Another objective of the present invention is to provide a controlcircuit and a method for detecting signals driving speakers to controloperation modes and a switching frequency of a charge pump.

Yet another objective of the present invention is to provide a controlcircuit and a method for performing self-test to an audio amplifier.

Still another objective of the present invention is to provide a chargepump and a control method thereof for arbitrarily adjusting a pumpedvoltage thereof.

A further objective of the present invention is to provide a charge pumpand a control method thereof for reducing the number of switchesthereof.

Still another objective of the present invention is to provide a controlmethod for a charge pump that is simpler to operate.

According to the present invention, a control circuit and a method foran audio amplifier detect a signal used to drive a speaker to control aswitching frequency and an operation mode of a charge pump, therebyimproving power efficiency. The control circuit may use a digitalinterface to automatically test whether the magnitude of the outputsignal of the audio amplifier is correct, thereby saving costs foranalog tests.

According to the present invention, a charge pump requires fewerswitches, to reduce costs and die area of an integrated circuit. Thecontrol method of the charge pump needs only a two phase control, so itsoperation is simpler. The charge pump and its control method cangenerate any possible positive and negative voltages, so have improvedadaptability.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objectives, features and advantages of the presentinvention will become apparent to those skilled in the art uponconsideration of the following description of the preferred embodimentsof the present invention taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a circuit diagram of a conventional two channel audioamplifier;

FIG. 2 is a waveform diagram of the positive voltage Vp, the negativevoltage Vn and the output signal SOR shown in FIG. 1;

FIG. 3 is a circuit diagram of a conventional dual mode charge pump;

FIG. 4 is a timing diagram of signals CS1, CS2, CS3, CS4, CS5, CS6, CS7and CS8 shown in FIG. 3;

FIG. 5 is a circuit diagram of an audio output apparatus using a controlcircuit according to the present invention;

FIG. 6 is a waveform diagram of the positive voltage Vp, the negativevoltage Vn and the output signal SOR shown in FIG. 5;

FIG. 7 is a waveform diagram showing the operation of the adaptivefrequency and voltage controller of FIG. 5;

FIG. 8 is a circuit diagram of an audio output apparatus using a controlcircuit according to a second embodiment of the present invention;

FIG. 9 is a circuit diagram of an embodiment for the amplitude levelsetting circuit shown in FIG. 5;

FIG. 10 is a circuit diagram of a first embodiment for the regulablecharge pump shown in FIG. 5;

FIG. 11 is a timing diagram of the regulable charge pump shown in FIG.10 in its first mode;

FIG. 12 is a circuit diagram of the regulable charge pump shown in FIG.10 in its first operation state of its first mode;

FIG. 13 is a circuit diagram of the regulable charge pump shown in FIG.10 in its second operation state of its first mode;

FIG. 14 is a timing diagram of the regulable charge pump shown in FIG.10 in its second mode;

FIG. 15 is a circuit diagram of the regulable charge pump shown in FIG.10 in its first operation state of its second mode;

FIG. 16 is a circuit diagram of the regulable charge pump shown in FIG.10 in its second operation state of its second mode;

FIG. 17 is a circuit diagram of a second embodiment for the regulablecharge pump shown in FIG. 5;

FIG. 18 is a timing diagram of the regulable charge pump shown in FIG.17 in its first mode;

FIG. 19 is a circuit diagram of the regulable charge pump shown in FIG.17 in its first operation state of its first mode;

FIG. 20 is a circuit diagram of the regulable charge pump shown in FIG.17 in its second operation state of its first mode;

FIG. 21 is a timing diagram of the regulable charge pump shown in FIG.17 in its second mode;

FIG. 22 is a circuit diagram of the regulable charge pump shown in FIG.17 in its first operation state of its second mode;

FIG. 23 is a circuit diagram of the regulable charge pump shown in FIG.17 in its second operation state of its second mode;

FIG. 24 is a circuit diagram of a third embodiment for the regulablecharge pump shown in FIG. 5;

FIG. 25 is a timing diagram of the regulable charge pump shown in FIG.24 in its first mode;

FIG. 26 is a circuit diagram of the regulable charge pump shown in FIG.24 in its first operation state of its first mode;

FIG. 27 is a circuit diagram of the regulable charge pump shown in FIG.24 in its second operation state of its first mode;

FIG. 28 is a timing diagram of the regulable charge pump shown in FIG.24 in its second mode;

FIG. 29 is a circuit diagram of the regulable charge pump shown in FIG.24 in its first operation state of its second mode;

FIG. 30 is a circuit diagram of the regulable charge pump shown in FIG.24 in its second operation state of its second mode;

FIG. 31 is a circuit diagram of an audio output apparatus using acontrol circuit according to a third embodiment of the presentinvention;

FIG. 32 is a circuit diagram of an embodiment for the regulable chargepump shown in FIG. 31;

FIG. 33 is a timing diagram of the regulable charge pump shown in FIG.32 in its first mode;

FIG. 34 is a circuit diagram of the regulable charge pump shown in FIG.32 in its first operation state of its first mode;

FIG. 35 is a circuit diagram of the regulable charge pump shown in FIG.32 in its second operation state of its first mode;

FIG. 36 is a timing diagram of the regulable charge pump shown in FIG.32 in its second mode;

FIG. 37 is a circuit diagram of the regulable charge pump shown in FIG.32 in its first operation state of its second mode;

FIG. 38 is a circuit diagram of the regulable charge pump shown in FIG.32 in its second operation state of its second mode;

FIG. 39 is a circuit diagram of the regulable charge pump shown in FIG.32 in its third operation state of its second mode;

FIG. 40 is a circuit diagram of an audio output apparatus using acontrol circuit according to a fourth embodiment of the presentinvention; and

FIG. 41 is a circuit diagram of an audio output apparatus using acontrol circuit according to a fifth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 5 shows an audio output apparatus using a control circuit 70according to the present invention in the audio amplifier of the audiooutput apparatus. In this embodiment, the amplifying circuits 10 and 13,power stages 12 and 14, speakers 16 and 18 and gain setting circuits 20are the same as shown in FIG. 1. The control circuit 70 includes aregulable charge pump 72, an adaptive frequency and voltage controller74, an amplitude level setting circuit 78, flying capacitors Cf1 and Cf2and output capacitors Co1 and Co2. The flying capacitor Cf1 has itsfirst and second terminals connected to the regulable charge pump 72,the flying capacitor Cf2 has its first terminals connected to a secondterminal of the flying capacitor Cf1, and its second terminal connectedto the regulable charge pump 72. The output capacitors Co1 and Co2 areconnected to output terminals 102 and 104 of the regulable charge pump72, respectively. The regulable charge pump 72 converts an input voltageVin into a variable positive voltage Vp and a variable negative voltageVn. Particularly, the regulable charge pump 72 has its operation modeand switching frequency determined by a clock signal Sck and a modeselect signal Sm provided by the adaptive frequency and voltagecontroller 74, instead of the gain setting circuit 20. The amplitudelevel setting circuit 78 provides a plurality of reference voltagesVr1-VrN for the adaptive frequency and voltage controller 74, where N isan integer. The adaptive frequency and voltage controller 74 detects theoutput signals SOR and SOL of the power stages 12 and 14, and comparesthe output signals SOR and SOL with the reference voltages Vr1-VrN toidentify the levels of the output signals SOR and SOL and in turn todetermine the clock signal Sck and the mode select signal Sm. Thedigital circuit 80 generates a signal Sd2 for the gain setting circuit20 according to a signal Sd1 provided by the adaptive frequency andvoltage controller 74. The gain setting circuit 20 generates the settingsignals G1, G2, G3 and G4 according to the signal Sd2 for controllingthe variable resistors 24, 26, 28, 30, 34, 36, 38, 40, 43, 44, 45, 46,47, 48, 49 and 50, to control the gains of the amplifying circuits 10and 13 and the power stages 12 and 14.

In the embodiment shown in FIG. 5, the adaptive frequency and voltagecontroller 74 further includes a design-for-test (DFT) circuit 76 toidentify whether the magnitude of the output signals SOR and SOL of theaudio amplifier is correct, so there is no need for an external ATE. TheDFT circuit 76 is a digital interface, helpful to save costs for analogtests. In addition, the adaptive frequency and voltage controller 74 maychange the switching frequency of the regulable charge pump 72 accordingto the levels of the output signals SOR and SOL, so that under the sameoperation mode, when the amplitudes of the output signals SOR and SOLreduce, the adaptive frequency and voltage controller 74 reduces theswitching frequency of the regulable charge pump 72 to improve powerefficiency. As shown in FIG. 6, in the condition that the operation modeof the regulable charge pump 72 is fixed, when the amplitude of theoutput signal SOR reduces, as shown at time t3, the adaptive frequencyand voltage controller 74 reduces the switching frequency of theregulable charge pump 72 to reduce the difference between the outputsignal SOR and the positive voltage Vp or the negative voltage Vnprovided by the regulable charge pump 72, thereby improving the powerefficiency of the audio amplifier.

FIG. 7 illustrates operation of the adaptive frequency and voltagecontroller 74 shown in FIG. 5, in which the waveform 82 represents theoutput signal SOR, the waveform 84 represents the output signal SOL, thewaveform 86 represents reference voltages Vr1-VrN, the waveform 88represents the detected output level, the eye diagram 90 represents theright channel frequency mode, the eye diagram 92 represents the leftchannel frequency mode, the eye diagram 94 represents the charge pumpmode, the waveform 96 represents the load decision value, and thewaveform 98 represents the reset value. Referring to FIGS. 5 and 7,during the period between time T1 and time T2, the adaptive frequencyand voltage controller 74 detects the level of the output signal SOR,and compares the output signal SOR with each of the reference voltagesVr1-VrN in order, to obtain the detected output level as shown by thewaveform 88. The detected output level between the time T1 and time T2only generates one pulse, meaning that the output signal SOR is greaterthan the reference voltage Vr1 but smaller than the reference voltageVr2, so the right channel frequency mode is set as FM1, as shown by theeye diagram 90. Similarly, if the detected output level has two pulses,meaning that the output signal SOR is greater than the reference voltageVr2 but smaller than the reference voltage Vr3, so the right channel orleft channel frequency mode is set as FM2. In the event that thedetected output level has three pulses, meaning that the output signalSOR is greater than the reference voltage Vr3 but smaller than thereference voltage Vr4, the right channel or left channel frequency modeis set as FM3; and so forth. In this embodiment, the frequency of thefrequency mode FM1 is lower than the frequency of the frequency modeFM2, the frequency of the frequency mode FM2 is lower than the frequencyof the frequency mode FM3, and so forth. During the period between timeT2 and time T3, the adaptive frequency and voltage controller 74compares the output signal SOL with each of the reference voltagesVr1-VrN in order, to identify the level of the output signal SOL,thereby obtaining the detected output level as shown by the waveform 88,so the left channel frequency mode is set as FM4, as shown by the eyediagram 92. At time T4, the load detection value is triggered, as shownby the waveform 96. Thus, the adaptive frequency and voltage controller74 will select the frequency mode FM4 that has a higher frequency amongthe right channel and left channel frequency modes as the charge pumpmode, as shown by the eye diagram 94, and accordingly generates theclock signal Sck and the mode select signal Sm that determine theswitching frequency and the operation mode of the regulable charge pump72. At time T5, the resetting value is triggered, as shown by thewaveform 98, so the adaptive frequency and voltage controller 74 willreset the right channel and left channel frequency mode as FM0.

As shown in FIG. 5, the input signals Sa2P and Sa2N of the power stage12 are related to the output signal SOR, and the input signals Sa4P andSa4N of the power stage 14 are related to the output signal SOL.Therefore, as shown in FIG. 8, for determining the clock signal Sck andthe mode select signal Sm, the adaptive frequency and voltage controller74 may detect the input terminal signals Sa2P, Sa2N, Sa4P and Sa4N ofthe power stage 12 and 14 instead, but not the output signals SOR andSOL. In the embodiment shown in FIG. 8, the DFT circuit 76 identifieswhether the magnitude of the output signals SOR and SOL of the audioamplifier is correct as done in the embodiment shown in FIG. 5. Theadaptive frequency and voltage controller 74 of the embodiment shown inFIG. 8 operates as the same way of the embodiment shown in FIG. 5. Inother embodiments, the adaptive frequency and voltage controller 74 maydetermine the clock signal Sck and the mode select signal Sm bydetecting other signals related to the output signals SOR and SOL.

FIG. 9 is an embodiment for the amplitude level setting circuit 78 shownin FIG. 5, which includes a plurality of serially connected resistorsRd1-RdN to divide a voltage Vs to generate the reference voltagesVr1-VrN for setting the corresponding switching modes FM0-FMN.

FIG. 10 is a first embodiment for the regulable charge pump 72 shown inFIG. 5, which includes an input terminal 100 to receive the inputvoltage Vin, an output terminal 102 connected to the output capacitorCo1 to provide the positive voltage Vp, an output terminal 104 connectedto the output capacitor Co2 to provide the negative voltage Vn, bondingpads 106 and 108 to be connected with the flying capacitor Cf1therebetween, bonding pads 110 and 108 to be connected with the flyingcapacitor Cf2 therebetween, a switch SW1 connected between the inputterminal 100 and the bonding pad 106 and controlled by a signal CS1_buf,a switch SW2 connected between the bonding pad 108 and a ground terminalGND and controlled by a signal CS2, a switch SW3 connected between thebonding pad 110 and the ground terminal GND and controlled by a signalCS3, a switch SW4 connected between the bonding pad 106 and the outputterminal 102 and controlled by a signal CS4, a switch SW5 connectedbetween the bonding pad 108 and the output terminal 102 and controlledby a signal CS5, a switch SW6 connected between the bonding pad 110 andthe output terminal 104 and controlled by a signal CS6, a clockgenerator 120 to determine the signals CS1, CS2, CS3, CS4, CS5 and CS6according to the clock signal Sck and the mode select signal Sm, adetector 112 to detect the voltage VB1 of the bonding pad 106 togenerate a voltage VB2, a reference voltage generator 114 to provide avariable reference voltage Vrefa, a comparator 116 to compare thevoltage VB2 with the reference voltage Vrefa to generate a comparisonsignal Scomp, and an AND gate 118 to determine the signal CS1_bufaccording to the signals Scomp and CS1. As shown in FIG. 10, thisregulable charge pump 72 has only six switches SW 1-SW6 and needs onlythree bonding pads to be connected with two flying capacitors Cf1 andCf2. In comparison with the charge pump 22 shown in FIG. 3, theregulable charge pump 72 shown in FIG. 10 saves two switches and onebonding pad, thereby saving costs and die area.

The dual mode charge pump 22 shown in FIG. 3 can only provide thepositive voltage Vp of either +Vin or +Vin/2 and the negative voltage Vnof either −Vin or −Vin/2, without capability of arbitrarily adjustingthe positive voltage Vp and the negative voltage Vn. The regulablecharge pump 72 shown in FIG. 10 uses the detector 112, reference voltagegenerator 114 and comparator 116 to control the voltage VB1 of thebonding pad 106, thereby generating the positive voltage Vp and thenegative voltage Vn at will. In further details, the detector 112includes serially connected resistors R1 and R2 to divide the voltage.VB1 to generate the voltage VB2, the reference voltage generator 114includes serially resistors R3 and R4 to divide the input voltage Vin togenerate the reference voltage Vrefa, where the resistor R4 is avariable resistor, and by changing the resistor R4, the referencevoltage Vrefa can be changed. When the clock generator 120 triggers thesignal CS1 to turn on the switch SW1, the voltage VB1 of the bonding pad106 increases, so the voltage VB2 also increases. When the voltage VB2becomes greater than the reference voltage Vrefa, meaning that thevoltage VB1 reaches a target value, the comparison signal Scompgenerated by the comparator 116 transits to low level and thus turns offthe switch SW1. Then when the voltage VB2 becomes smaller than thevoltage Vrefa, the comparator 116 will again assert the comparisonsignal Scomp to high level. By this way, changing the reference voltageVrefa can control the voltage VB1, thereby adjusting the positivevoltage Vp and the negative voltage Vn at will.

FIG. 11 is a timing diagram of the regulable charge pump 72 shown inFIG. 10 in its first mode. When the regulable charge pump 72 is in itsfirst operation state of its first mode, as during the period betweentime tm11 and time tm12, the signals CS1_buf, CS3, CS4 and CS5 turn onthe switches SW1, SW3, SW4 and SW5, and the signals CS2 and CS6 turn offthe switches SW2 and SW6. As shown in FIG. 12, the first terminal 122 ofthe flying capacitor Cf is connected to its second terminal 124, thefirst terminal 126 of the flying capacitor Cf2 is connected to theoutput capacitor Co1 and the input terminal 100, and the second terminal128 of the flying capacitor Cf2 is connected to the ground terminal GND.In this case the first terminal 122 and the second terminal 124 of theflying capacitor Cf1 become short circuit to each other, so the flyingcapacitor Cf1 is disabled to stop working, and the flying capacitor Cf2is connected in parallel with the output capacitor Co1, so the inputvoltage Vin charges the flying capacitor Cf2 and the output capacitorCo1 to increase the voltage VB1, thereby generating the positive voltageVp=VB1. When the voltage VB1 (or the positive voltage Vp) reaches atarget value, i.e. VB2=Vrefa, the regulable charge pump 72 enters itssecond operation state of the first mode.

When the regulable charge pump 72 is in its second operation state ofthe first mode, as during the period between the time tm12 and time tm13as shown in FIG. 11, the signals CS1_buf, CS3, CS4 and CS5 turn off theswitches SW1, SW3, SW4 and SW5, and the signals CS2 and CS6 turn on theswitches SW2 and SW6. As shown in FIG. 13, the first terminal 122 of theflying capacitor Cf1 is floating, the first terminal 126 of the flyingcapacitor Cf2 is connected to the ground terminal GND, and the secondterminal 128 of the flying capacitor Cf2 is connected to the outputcapacitor Co2. In this case the first terminal 122 of the flyingcapacitor Cf1 is floating, so the flying capacitor Cf1 is disabled tostop working, and the flying capacitor Cf2 charges the output capacitorCo2, thereby generating the negative voltage Vp=−VB1.

FIG. 14 is a timing diagram of the regulable charge pump 72 shown inFIG. 10 in its second mode. When the regulable charge pump 72 is in itsfirst operation state of the second mode, as during the period betweentime tm21 and time tm22, the signals CS1_buf, CS3 and CS5 turn on theswitches SW1, SW3 and SW5, and the signals CS2, CS4 and CS6 turn off theswitches SW2, SW4 and SW6. As shown in FIG. 15, the first terminal 122of the flying capacitor Cf1 is connected to the input terminal 100, thefirst terminal 126 of the flying capacitor Cf2 is connected to thesecond terminal 124 of the flying capacitor Cf1 and the output capacitorCo1, and the second terminal of the flying capacitor Cf2 is connected tothe ground terminal GND. In this case the input voltage Vin charges theflying capacitors Cf1 and Cf2 and the output capacitor Co1, to generatethe voltage VB1 and the positive voltage Vp. Assuming that, in thisembodiment, Cf1=Cf2+Co1, the flying capacitors Cf1 and Cf2 and theoutput capacitor Co1 will divide the voltage VB1 to generate thepositive voltage Vp=VB1/2. When the voltage VB1 reaches a target value,i.e. VB2=Vrefa, the regulable charge pump 72 enters the second operationstate of the second mode.

When the regulable charge pump 72 is in the second operation state ofthe second mode, as during the period between time tm22 and time tm23,the signals CS1_buf, CS3 and CS5 turn off the switches SW1, SW3 and SW5,and the signals CS2, CS4 and CS6 turn on the switches SW2, SW4 and SW6.As shown in FIG. 16, the first terminal 122 of the flying capacitor Cf1is connected to the output capacitor Co1, the second terminal 124 of theflying capacitor Cf1 and the first terminal 126 of the flying capacitorCf2 are both connected to the ground terminal GND, and the secondterminal 128 of the flying capacitor Cf2 is connected to the outputcapacitor Co2. In this case the flying capacitor Cf2 charges the outputcapacitor Co2 to generate the negative voltage Vn=−VB1/2.

FIG. 17 is a second embodiment for the regulable charge pump 72 shown inFIG. 5. In addition to the input terminal 100, output terminals 102 and104, bonding pads 106, 108 and 110, detector 112, reference voltagegenerator 114, comparator 116, AND gate 118, clock generator 120 andswitches SW1-SW6 as those shown in FIG. 10, a switch SW7 is furtherincluded and connected between the bonding pad 106 and the groundterminal GND. The clock generator 120 also determines a signal CS7according to the clock signal Sck and the mode select signal Sm tocontrol the switch SW7. The regulable charge pump 72 shown in FIG. 17has only seven switches and needs only three bonding pads for connectionwith two flying capacitors Cf1 and Cf2. In comparison with the chargepump 22 shown in FIG. 3, the regulable charge pump 72 shown in FIG. 17saves one switch and one bonding pad, thereby saving costs and die areaof an integrated circuit.

FIG. 18 is a timing diagram of the regulable charge pump 72 shown inFIG. 17 in its first mode. When the regulable charge pump 72 is in thefirst operation state of the first mode, as during the period betweentime tm14 and time tm15, the signals CS1_buf, CS3 and CS4 turn on theswitches SW1, SW3 and SW4, and the signals CS2, CS5, CS6 and CS7 turnoff the switch SW2, SW5, SW6 and SW7. As shown in FIG. 19, the firstterminal 122 of the flying capacitor Cf1 is connected to the inputterminal 100 and the output capacitor Co1, the second terminal 124 ofthe flying capacitor Cf1 is connected to the first terminal 126 of theflying capacitor Cf2, and the second terminal 128 of the flyingcapacitor Cf2 is connected to the ground terminal GND. In this case theinput voltage Vin charges the flying capacitors Cf1 and Cf2 and theoutput capacitor Co1 to generate the positive voltage Vp=VB1. When thevoltage VB 1 (or the positive voltage Vp) reaches a target value, i.e.VB2=Vrefa, the regulable charge pump 72 enters the second operationstate of the first mode.

When the regulable charge pump 72 is in the second operation state ofthe first mode, as during the period between time tm15 and time tm16,the signals CS1_buf, CS2, CS3, CS4 and CS5 turn off the switches SW1,SW2, SW3, SW4 and SW5, and the signals CS6 and CS7 turn on the switchesSW6 and SW7. As shown in FIG. 20, the first terminal 122 and the secondterminal 124 of the flying capacitor Cf1 are connected to the groundterminal GND and the first terminal 126 of the flying capacitor Cf2,respectively, and the second terminal 128 of the flying capacitor Cf2 isconnected to the output capacitor Co2. In this case the flyingcapacitors Cf1 and Cf2 charges the output capacitor Co2 to generate thenegative voltage Vn=−VB1.

FIG. 21 is a timing diagram of the regulable charge pump 72 shown inFIG. 17. When the regulable charge pump 72 is in the first operationstate of the second mode, as during the period between time tm24 andtime tm25, the signals CS1_buf, CS3 and CS5 turn on the switches SW1,SW3 and SW5, and the signals CS2, CS4, CS6 and CS7 turn off the switchesSW2, SW4, SW6 and SW7. As shown in FIG. 22, the first terminal 122 ofthe flying capacitor Cf1 is connected to the input terminal 100, thesecond terminal 124 of the flying capacitor Cf1 is connected to theoutput capacitor Co1 and the first terminal 126 of the flying capacitorCf2, and the second terminal 128 of the flying capacitor Cf2 isconnected to the ground terminal GND. In this case the input voltage Vincharges the flying capacitors Cf1 and Cf2 and the output capacitor Co1to generate the voltage VB1 and the positive voltage Vp. Assuming that,in this embodiment, Cf1=Cf2+Co1, the flying capacitors Cf1 and Cf2 andthe output capacitor Co1 will divide the voltage VB1 to generate thepositive voltage Vp=VB1/2. When the voltage VB1 reaches a target value,i.e. VB2=Vrefa, the regulable charge pump 72 enters the second operationstate of the second mode.

When the regulable charge pump 72 is in the second operation state ofthe second mode, as during the period between time tm25 and time tm26,the signals CS1_buf, CS3, CS5 and CS7 turn off the switches SW1, SW3,SW5 and SW7, and the signals CS2, CS4 and CS6 turn on the switches SW2,SW4 and SW6. As shown in FIG. 23, the first terminal 122 and the secondterminal 124 of the flying capacitor Cf1 are connected to the outputcapacitor Co1 and the ground terminal GND, respectively, and the firstterminal 126 and the second terminal 128 of the flying capacitor Cf2 areconnected to the ground terminal GND and the output capacitor Co2,respectively. In this case the flying capacitor Cf2 charges the outputcapacitor Co2 to generate the negative voltage Vn=−VB1/2.

FIG. 24 is a third embodiment for the regulable charge pump 72 shown inFIG. 5. Similar to the circuit shown in FIG. 17, it also has the inputterminal 100, output terminals 102 and 104, bonding pads 106, 108 and110, detector 112, reference voltage generator 114, comparator 116, ANDgate 118, clock generator 120 and switches SW1-SW7; however, the switchSW7 is connected between the input terminal 100 and the bonding pad 108.In the embodiment shown in FIG. 24, the clock generator 120 determinesthe signals CS1, CS2, CS3, CS4, CS5, CS6 and CS7 according to the clocksignal Sck and the mode select signal Sm, and the signals CS2, CS3, CS4,CS5 and CS6 control the switches SW2, SW3, SW4, SW5 and SW6,respectively. When the regulable charge pump 72 operates in its firstmode, the switch SW1 is controlled by the signal CS1, and the AND gate118 generates the signal CS7_buf according to the comparison signalScomp and the signal CS7 to control the switch SW7. At this time thedetector 112 detects the voltage VB3 of the bonding pad 108 to generatethe voltage VB2. When the voltage VB2 becomes greater than the referencevoltage Vrefa, meaning that the voltage VB3 reaches a target value, thecomparator 116 turns off the comparison signal Scomp to turn off theswitch SW7. When the regulable charge pump 72 operates in its secondmode, the switch SW7 is controlled by the signal CS7, and the AND gate118 generates the signal CS1_buf according to the comparison signalScomp and the signal CS1 to control the switch SW1. At this time thedetector 112 detects the voltage VB1 of the bonding pad 106 to generatethe voltage VB2. When the voltage VB2 becomes greater than the referencevoltage Vrefa, meaning that the voltage VB1 reaches a target value, thecomparator 116 turns off the comparison signal Scomp to turn off theswitch SW1. The regulable charge pump 72 shown in FIG. 24 has only sevenswitches and needs only three bonding pads for connection with twoflying capacitors Cf1 and Cf2. In comparison with the charge pump 22shown in FIG. 3, the regulable charge pump 72 shown in FIG. 24 saves oneswitch and one bonding pad, thereby saving costs and die area of anintegrated circuit.

FIG. 25 is a timing diagram of the regulable charge pump 72 shown inFIG. 24 in its first mode. When the regulable charge pump 72 is in thefirst operation state of the first mode, as during the period betweentime tm17 and time tm18, the signals CS3, CS5 and CS7_buf turn on theswitches SW3, SW5 and SW7, and the signals CS1, CS2, CS4 and CS6 turnoff the switches SW1, SW2, SW4 and SW6. As shown in FIG. 26, the firstterminal 122 of the flying capacitor Cf1 is floating. The first terminal126 of the flying capacitor Cf2 is connected to the input terminal 100and the output capacitor Co1, and the second terminal 128 of the flyingcapacitor Cf2 is connected to the ground terminal GND. In this case thefirst terminal 122 of the flying capacitor Cf1 is floating, so theflying capacitor Cf1 is disabled to stop working, and the input voltageVin charges the flying capacitor Cf2 and the output capacitor Co1,thereby generating the positive voltage Vp=VB3. The detector 112 detectsthe voltage VB3 to generate the voltage VB2. When the voltage VB3 (orthe positive voltage Vp) reaches a target value, i.e. VB2=Vrefa, theregulable charge pump 72 enters the second operation state of the firstmode.

When the regulable charge pump 72 is in the second operation state ofthe first mode, as during the period between time tm18 and time tm19,the signals CS1, CS3, CS4, CS5 and CS7_buf turn off the switches SW1,SW3, SW4, SW5 and SW7, and the signals CS2 and CS6 turn on the switchesSW2 and SW6. As shown in FIG. 27, the first terminal 122 of the flyingcapacitor Cf1 is floating, and the first terminal 126 and the secondterminal 128 of the flying capacitor Cf2 are connected to the groundterminal GND and the output capacitor Co2, respectively. In this casethe first terminal 122 of the flying capacitor Cf1 is floating, so theflying capacitor Cf1 is disabled to stop working, and the flyingcapacitor Cf2 charges the output capacitor Co2, thereby generatingnegative voltage Vn=−VB3.

FIG. 28 is a timing diagram of the regulable charge pump 72 shown inFIG. 24 in the second mode. When the regulable charge pump 72 is in thefirst operation state of the second mode, as during the period betweentime tm27 and time tm28, the signals CS1_buf, CS3 and CS5 turn on theswitches SW1, SW3 and SW5, and the signals CS2, CS4, CS6 and CS7 turnoff the switches SW2, SW4, SW6 and SW7. As shown in FIG. 29, the firstterminal 122 of the flying capacitor Cf1 is connected to the inputterminal 100, the second terminal 124 of the flying capacitor Cf1 isconnected to the output capacitor Co1 and the first terminal 126 of theflying capacitor Cf2, and the second terminal 128 of the flyingcapacitor Cf2 is connected to the ground terminal GND. In this case theinput voltage Vin charges the flying capacitors Cf1 and Cf2 and theoutput capacitor Co1 to generate the voltage VB1 and the positivevoltage Vp. Assuming that, in this embodiment, Cf1=Cf2+Co1, the flyingcapacitors Cf1 and Cf2 and the output capacitor Co1 will divide thevoltage VB1 to generate the positive voltage Vp=VB 1/2. The detector 112detects the voltage VB1 to generate the voltage VB2. When the voltageVB1 reaches a target value, i.e. VB2=Vrefa, the regulable charge pump 72enters the second operation state of the second mode.

When the regulable charge pump 72 is in its second operation state ofits second mode, as during the period between time tm28 and time tm29,the signals CS1_buf, CS3, CS5 and CS7 turn off the switches SW1, SW3,SW5 and SW7, and the signals CS2, CS4 and CS6 turn on the switches SW2,SW4 and SW6. As shown in FIG. 30, the first terminal 122 and the secondterminal 124 of the flying capacitor Cf1 are connected to the outputcapacitor Co1 and the ground terminal GND, respectively, and the firstterminal 126 and the second terminal 128 of the flying capacitor Cf2 areconnected to the ground terminal GND and the output capacitor Co2. Inthis case the flying capacitor Cf2 charges the output capacitor Co2 togenerate the negative voltage Vn=−VB1/2.

As shown in FIGS. 11, 14, 18, 21, 25 and 28, the regulable charge pump72 shown in FIG. 10, 17 or 24 uses fewer switches and bonding pads, andonly needs two phase control for generating the positive voltage Vp andthe negative voltage Vn, thereby simplifying the operation.

FIG. 31 is a third embodiment for the control circuit 70 according tothe present invention. Similar to the circuit shown in FIG. 5, thecontrol circuit 70 in this embodiment also includes the regulable chargepump 72, adaptive frequency and voltage controller 74, amplitude levelsetting circuit 78, flying capacitors Cf1 and Cf2 and output capacitorsCo1 and Cot, while the first terminal of the flying capacitor Cf2 is notconnected to the second terminal of the flying capacitor Cf1, and thesecond terminal of the flying capacitor Cf2 is connected to the groundterminal GND. The adaptive frequency and voltage controller 74 shown inFIG. 31 may be similar to its counterpart shown in FIG. 8, indetermining the clock signal Sck and the mode select signal Sm bydetecting the signals Sa2P, Sa2N, Sa4P and Sa4N that are related to theoutput signals SOR and SOL.

FIG. 32 shows an embodiment for the regulable charge pump 72 shown inFIG. 31. Similar to the circuit shown in FIG. 10, the regulable chargepump 72 in this embodiment also includes the input terminal 100, outputterminals 102 and 104, bonding pads 106, 108 and 110, detector 112,reference voltage generator 114, comparator 116, AND gate 118 and clockgenerator 120, while the bonding pad 108 is not connected to the flyingcapacitor Cf2, and the clock generator 120 is configured to generate thesignals CS1, CS2, CS3, CS4, CS5, CS6 and CS7 according to the clocksignal Sck and the mode select signal Sm. The regulable charge pump 72shown in FIG. 32 further includes a switch SW1 connected between theinput terminal 100 and the bonding pad 106 and controlled by the signalCS1_buf, a switch SW2 connected between the bonding pad 108 and theground terminal GND and controlled by the signal CS2, a switch SW3connected between the bonding pad 106 and the output terminal 102 andcontrolled by the signal CS3, a switch SW4 connected between the bondingpad 106 and the ground terminal GND and controlled by the signal CS4, aswitch SW5 connected between the bonding pad 108 and the output terminal104 and controlled by the signal CS5, a switch SW6 connected between thebonding pads 108 and 110 and controlled by the signal CS6, and a switchSW7 connected between the bonding pads 106 and 110 and controlled by thesignal CS7. The regulable charge pump 72 shown in FIG. 32 has only sevenswitches and needs only three bonding pads for connection with twoflying capacitors Cf1 and Cf2. In comparison with the charge pump 22shown in FIG. 3, the regulable charge pump 72 shown in FIG. 32 saves oneswitch and one bonding pad, thereby saving costs and die area of anintegrated circuit.

FIG. 33 is a timing diagram of the regulable charge pump 72 shown inFIG. 32 in its first mode. When the regulable charge pump 72 is in itsfirst operation state of its first mode, as during the period betweentime tm110 and time tm111, the signals CS1_buf, CS2 and CS3 turn on theswitches SW1, SW2 and SW3, and the signals CS4, CS5, CS6 and CS7 turnoff the switches SW4, SW5, SW6 and SW7. As shown in FIG. 34, the firstterminal 122 of the flying capacitor Cf1 is connected to the inputterminal 100 and the output capacitor Co1, the second terminal 124 ofthe flying capacitor Cf1 is connected to the ground terminal GND, andthe first terminal 126 of the flying capacitor Cf2 whose second terminal128 is grounded is floating. In this case the first terminal 126 of theflying capacitor Cf2 is floating, so the flying capacitor Cf2 isdisabled to stop working, and the input voltage Vin charges the flyingcapacitor Cf1 and the output capacitor Co1 to generate the positivevoltage Vp=VB1. When the voltage VB1 (or the positive voltage Vp)reaches a target value, i.e. VB2=Vrefa, the regulable charge pump 72enters its second operation state of its first mode.

When the regulable charge pump 72 is in its second operation state ofits first mode, as during the period between time tm111 and time tm112,the signals CS1_buf, CS2, CS3, CS6 and CS7 turn off the switches SW1,SW2, SW3, SW6 and SW7, and the signals CS4 and CS5 turn on the switchesSW4 and SW5. As shown in FIG. 35, the first terminal 122 and the secondterminal 124 of the flying capacitor Cf1 are connected to the groundterminal GND and the output capacitor Co2, respectively, and the firstterminal 126 of the flying capacitor Cf2 is floating. In this case thefirst terminal 126 of the flying capacitor Cf2 is floating, so theflying capacitor Cf2 is disabled to stop working, and the flyingcapacitor Cf1 charges the output capacitor Co2 to generate the negativevoltage Vn=−VB1.

FIG. 36 is a timing diagram of the regulable charge pump 72 shown inFIG. 32 in its second mode. When the regulable charge pump 72 in itsfirst operation state of its second mode, as during the period betweentime tm210 and time tm211, the signals CS1_buf and CS6 turn on theswitches SW1 and SW6, and the signals CS2, CS3, CS4, CS5 and CS7 turnoff the switches SW2, SW3, SW4, SW5 and SW7. As shown in FIG. 37, thefirst terminal 122 and second terminal 124 of the flying capacitor Cf1are connected to the input terminal 100 and the first terminal 126 ofthe flying capacitor Cf2, respectively. In this case the input voltageVin charges the flying capacitors Cf1 and Cf2 to generate the voltageVB1. Assuming that in the embodiment Cf1=Cf2, the across voltage of eachof the flying capacitors Cf1 and Cf2 will be VB1/2. When the voltage VB1reaches a target value, i.e. VB2=Vrefa, the regulable charge pump 72enters its second operation state of its second mode.

When the regulable charge pump 72 is in its second operation state ofits second mode, as during the period between time tm211 and time tm212,the signals CS1_buf, CS4, CS5 and CS6 turn off the switches SW1, SW4,SW5 and SW6 and the signals CS2, CS3 and CS7 turn on the switches SW2,SW3 and SW7. As shown in FIG. 38, the first terminal 122 and secondterminal 124 of the flying capacitor Cf1 are connected to the outputcapacitor Co1 and the ground terminal GND, respectively, and the firstterminal 126 of the flying capacitor Cf2 is connected to the outputcapacitor Co1. In this case the flying capacitors Cf1 and Cf2 charge theoutput capacitor Co1 to generate the positive voltage Vp=VB1/2.

When the regulable charge pump 72 is in its third operation state of itssecond mode, as during the period between time tm212 and time tm213, thesignals CS1_buf, CS2, CS3, CS6 and CS7 turn off the switches SW1, SW2,SW3, SW6 and SW7, and the signals CS4 and CS5 turn on the switches SW4and SW5. As shown in FIG. 39, the first terminal 122 and second terminal124 of the flying capacitor Cf1 are connected to the ground terminal GNDand the output capacitor Co2, respectively, and the first terminal 126of the flying capacitor Cf2 is floating. In this case the first terminal126 of the flying capacitor Cf2 is floating, so the flying capacitor Cf2is disabled to stop working, and the flying capacitor Cf1 charges theoutput capacitor Co2 to generate the negative voltage Vn=−VB1/2.

In applications where free adjustment of either Vp or Vn is notrequired, the detector 112, reference voltage generator 114, comparator116 and AND gate 118 shown in FIGS. 10, 17, 24 and 32 can be removed forsaving costs and die area of an integrated circuit.

FIG. 40 is a fourth embodiment for the control circuit 70 according tothe present invention. In addition to the regulable charge pump 72,amplitude level setting circuit 78, flying capacitors Cf1 and Cf2 andoutput capacitors Co1 and Co2 as shown in FIG. 5, the control circuit 70in this embodiment includes an adaptive voltage controller 130 and aswitching frequency controller 132. The adaptive voltage controller 130detects the output signals SOR and SOL, and compares the output signalsSOR and SOL with the reference voltages Vr1-VrN to identify the levelsof the output signals SOR and SOL and in turn to determine the modeselect signal Sm. The adaptive voltage controller 130 includes a DFTcircuit 76 to identify whether the magnitude of the output signals SORand SOL is correct. The switching frequency controller 132 determinesthe clock signal Sck according to the setting signals G2 and G4 providedby the gain setting circuit 20. The regulable charge pump 72 switchesthe operation mode according to the mode select signal Sm, and operatesat the switching frequency determined by the clock signal Sck. Theadaptive voltage controller 130 shown in FIG. 40 may be similar to theadaptive frequency and voltage controller 74 shown in FIG. 8, indetermining the mode select signal Sm by detecting the signals Sa2P,Sa2N, Sa4P and Sa4N of the input terminals of the power stages 12 and14. The regulable charge pump 72 shown in FIG. 40 may have the circuitas shown in FIG. 10, 17 or 24.

The adaptive frequency and voltage controller 74 shown in FIG. 31 may bereplaced by the adaptive voltage controller 130 and the switchingfrequency controller 132 shown in FIG. 40, to control the operation modeand the switching frequency of the regulable charge pump 72, as shown inFIG. 41. The adaptive voltage controller 130 shown in FIG. 41 may besimilar to the adaptive frequency and voltage controller 74 shown inFIG. 8, in determining the mode select signal Sm by detecting thesignals Sa2P, Sa2N, Sa4P and Sa4N of the input terminals of the powerstages 12 and 14. The regulable charge pump 72 of FIG. 41 may be thesame as that shown in FIG. 32.

While the present invention has been described in conjunction withpreferred embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and scopethereof as set forth in the appended claims.

What is claimed is:
 1. A control circuit for an audio amplifierincluding a power stage to generate an output signal according to asignal at an input terminal thereof for driving one or more speakers,the control circuit comprising: a charge pump connected to the powerstage, operative to convert an input voltage into a variable positivevoltage and a variable negative voltage for supplying to the power stageto generate the output signal; and an adaptive frequency and voltagecontroller connected to the charge pump, operative to detect a level ofa signal related to the output signal to generate a clock signal and amode select signal for the charge pump, thereby determining a switchingfrequency and an operation mode of the charge pump.
 2. The controlcircuit of claim 1, wherein the adaptive frequency and voltagecontroller detects a level of the output signal to generate the clocksignal and the mode select signal.
 3. The control circuit of claim 1,wherein the adaptive frequency and voltage controller detects a level ofa signal at an input terminal of the power stage to generate the clocksignal and the mode select signal.
 4. The control circuit of claim 1,further comprising an amplitude level setting circuit connected to theadaptive frequency and voltage controller, operative to provide aplurality of reference voltages to the adaptive frequency and voltagecontroller, wherein the plurality of reference voltages are comparedwith the signal related to the output signal to identify the level ofthe signal related to the output signal.
 5. The control circuit of claim1, wherein the adaptive frequency and voltage controller comprises adesign-for-test circuit operative to test the output signal foridentifying whether a magnitude of the output signal is correct.
 6. Thecontrol circuit of claim 1, wherein the charge pump comprises: a firstbonding pad and a second bonding pad for a first flying capacitorconnected therebetween; a third bonding pad and the second bonding padfor a second flying capacitor connected therebetween; an input terminalreceiving the input voltage; a first output terminal connected to afirst output capacitor, providing the positive voltage; a second outputterminal connected to a second output capacitor, providing the negativevoltage; a first switch connected between the input terminal and thefirst bonding pad; a second switch connected between the second bondingpad and a ground terminal; a third switch connected between the thirdbonding pad and the ground terminal; a fourth switch connected betweenthe first bonding pad and the first output terminal; a fifth switchconnected between the second bonding pad and the first output terminal;a sixth switch connected between the third bonding pad and the secondoutput terminal; and a clock generator connected to the adaptivefrequency and voltage controller and the first through sixth switches,operative to generate first through sixth signals according to the clocksignal and the mode select signal to control the first through sixthswitches, respectively.
 7. The control circuit of claim 6, wherein thecharge pump further comprises: a detector connected to the first bondingpad, detecting a first voltage of the first bonding pad to generate asecond voltage related to the first voltage; a reference voltagegenerator providing a variable reference voltage for controlling thepositive voltage or the negative voltage; and a comparator connected tothe detector and the reference voltage generator, comparing the secondvoltage with the reference voltage to turn off the first switch when thesecond voltage becomes greater than the reference voltage.
 8. Thecontrol circuit of claim 7, wherein during a first operation state of afirst mode of the charge pump, the first, third, fourth and fifthswitches are turned on and the second and sixth switches are turned off;during a second operation state of the first mode of the charge pump,the first, third, fourth and fifth switches are turned off and thesecond and sixth switches are turned on; during a first operation stateof a second mode of the charge pump, the first, third and fifth switchesare turned on and the second, fourth and sixth switches are turn off;and during a second operation state of the second mode of the chargepump, the first, third and fifth switches are turned off and the second,fourth and the sixth switches are turned on.
 9. The control circuit ofclaim 7, wherein the charge pump further comprises a seventh switchconnected between the first bonding pad and the ground terminal,controlled by a seventh signal determined by the clock signal and themode select signal by the clock generator.
 10. The control circuit ofclaim 9, wherein during a first operation state of a first mode of thecharge pump, the first, third and fourth switches are turned on and thesecond, fifth, sixth and seventh switches are turned off; during asecond operation state of the first mode of the charge pump, the firstthrough fifth switches are turned off and the sixth and seventh switchesare turned on; during a first operation state of a second mode of thecharge pump, the first, third and fifth switches are turned on and thesecond, fourth, sixth and seventh switches are turned off; and during asecond operation state of the second mode of the charge pump, the first,third, fifth and seventh switches are turned off and the second, fourthand sixth switches are turn on.
 11. The control circuit of claim 6,wherein during a first operation state of a first mode of the chargepump, the first, third, fourth and fifth switches are turned on and thesecond and sixth switches are turned off; during a second operationstate of the first mode of the charge pump, the first, third, fourth andfifth switches are turned off and the second and sixth switches areturned on; during a first operation state of a second mode of the chargepump, the first, third and fifth switches are turned on and the second,fourth and sixth switches are turn off; and during a second operationstate of the second mode of the charge pump, the first, third and fifthswitches are turned off and the second, fourth and sixth switches areturned on.
 12. The control circuit of claim 6, wherein the charge pumpfurther comprises a seventh switch connected between the first bondingpad and the ground terminal, controlled by a seventh signal determinedby the clock signal and the mode select signal by the clock generator.13. The control circuit of claim 12, wherein during a first operationstate of a first mode of the charge pump, the first, third and fourthswitches are turned on and the second, fifth, sixth and seventh switchesare turned off; during a second operation state of the first mode of thecharge pump, the first through fifth switches are turned off and thesixth and seventh switches are turned on; during a first operation stateof a second mode of the charge pump, the first, third and fifth switchesare turned on and the second, fourth, sixth and seventh switches areturned off; and during a second operation state of the second mode ofthe charge pump, the first, third, fifth and seventh switches are turnedoff and the second, fourth and sixth switches are turn on.
 14. Thecontrol circuit of claim 6, wherein the charge pump further comprises aseventh switch connected between the input terminal and the secondbonding pad, controlled by a seventh signal determined by the clocksignal and the mode select signal by the clock generator.
 15. Thecontrol circuit of claim 14, wherein the charge pump further comprises:a detector connected to the first and second bonding pads, detecting afirst voltage of the first bonding pad during a second mode of thecharge pump to generate a second voltage, and detecting a third voltageof the second bonding pad during a first mode of the charge pump togenerate the second voltage; a reference voltage generator providing avariable reference voltage for controlling the positive voltage or thenegative voltage; and a comparator connected to the detector and thereference voltage generator, comparing the second voltage with thereference voltage to turn off the seventh switch during the first modeof the charge pump when the second voltage becomes greater than thereference voltage, and to turn off the first switch during the secondmode of the charge pump when the second voltage becomes greater than thereference voltage.
 16. The control circuit of claim 15, wherein during afirst operation state of the first mode of the charge pump, the first,second, fourth and sixth switches are turned off and the third, fifthand seventh switches are turned on; during a second operation state ofthe first mode of the charge pump, the first, third, fourth, fifth andseventh switches are turned off and the second and sixth switches areturned on; during a first operation state of the second mode of thecharge pump, the first, third and fifth switches are turned on and thesecond, fourth, sixth and seventh switches are turned off; and during asecond operation state of the second mode of the charge pump, the first,third, fifth, seventh switches are turned off and the second, fourth andsixth switches are turned on.
 17. The control circuit of claim 14,wherein during a first operation state of a first mode of the chargepump, the first, second, fourth and sixth switches are turned off andthe third, fifth and seventh switches are turned on; during a secondoperation state of the first mode of the charge pump, the first, third,fourth, fifth and seventh switches are turned off and the second andsixth switches are turned on; during a first operation state of a secondmode of the charge pump, the first, third and fifth switches are turnedon and the second, fourth, sixth and seventh switches are turned off;and during a second operation state of the second mode of the chargepump, the first, third, fifth, seventh switches are turned off and thesecond, fourth and sixth switches are turned on.
 18. The control circuitof claim 1, wherein the charge pump comprises: a first bonding pad and asecond bonding pad for a first flying capacitor connected therebetween;a third bonding pad connected to a second flying capacitor; an inputterminal receiving the input voltage; a first output terminal connectedto a first output capacitor, providing the positive voltage; a secondoutput terminal connected to a second output capacitor, providing thenegative voltage; a first switch connected between the input terminaland the first bonding pad; a second switch connected between the secondbonding pad and a ground terminal; a third switch connected between thefirst bonding pad and the first output terminal; a fourth switchconnected between the first bonding pad and the ground terminal; a fifthswitch connected between the second bonding pad and the second outputterminal; a sixth switch connected between the second bonding pad andthe third bonding pad; a seventh switch connected between the firstbonding pad and the third bonding pad; and a clock generator connectedto the adaptive frequency and voltage controller and the first throughseventh switches, operative to generate first through seventh signalsaccording to the clock signal and the mode select signal to control thefirst through seventh switches, respectively.
 19. The control circuit ofclaim 18, wherein the charge pump further comprises: a detectorconnected to the first bonding pad, detecting a first voltage of thefirst bonding pad to generate a second voltage related to the firstvoltage; a reference voltage generator providing a variable referencevoltage for controlling the positive voltage or the negative voltage;and a comparator connected to the detector and the reference voltagegenerator, comparing the second voltage with the reference voltage toturn off the first switch when the second voltage becomes greater thanthe reference voltage.
 20. The control circuit of claim 19, whereinduring a first operation state of a first mode of the charge pump, thefirst through third switches are turned on and the fourth throughseventh switches are turned off; during a second operation state of thefirst mode of the charge pump, the first, second, third, sixth andseventh switches are turned off and the fourth and fifth switches areturned on; during a first operation state of a second mode of the chargepump, the first and sixth switches are turned on and the second, third,fourth, fifth and seventh switches are turned off; during a secondoperation state of the second mode of the charge pump, the first,fourth, fifth and sixth switches are turned off and the second, thirdand seventh switches are turned on; and during a third operation stateof the second mode of the charge pump, the first, second, third, sixthand seventh switches are turned off and the fourth and fifth switchesare turned on.
 21. The control circuit of claim 18, wherein during afirst operation state of a first mode of the charge pump, the firstthrough third switches are turned on and the fourth through seventhswitches are turned off; during a second operation state of the firstmode of the charge pump, the first, second, third, sixth and seventhswitches are turned off and the fourth and fifth switches are turned on;during a first operation state of a second mode of the charge pump, thefirst and sixth switches are turned on and the second, third, fourth,fifth and seventh switches are turned off; during a second operationstate of the second mode of the charge pump, the first, fourth, fifthand sixth switches are turned off and the second, third and seventhswitches are turned on; and during a third operation state of the secondmode of the charge pump, the first, second, third, sixth and seventhswitches are turned off and the fourth and fifth switches are turned on.22. A control method for an audio amplifier including a power stage togenerate an output signal according to a signal at an input terminalthereof for driving one or more speakers, the control method comprising:A.) converting an input voltage into a variable positive voltage and avariable negative voltage by a charge pump for supplying to the powerstage to generate the output signal; and B.) detecting a level of asignal related to the output signal for generating a clock signal and amode select signal to determine a switching frequency and an operationmode of the charge pump.
 23. The control method of claim 22, wherein thestep B comprises detecting a level of the output signal to generate theclock signal and the mode select signal.
 24. The control method of claim22, wherein the step B comprises detecting a level of the signal at theinput terminal of the power stage to generate the clock signal and themode select signal.
 25. The control method of claim 22, wherein the stepB comprises providing a plurality of reference voltages to be comparedwith the signal related to the output signal to identify the level ofthe signal related to the output signal.
 26. The control method of claim22, further comprising testing the output signal to identify whether amagnitude of the output signal is correct.
 27. The control method ofclaim 22, wherein the step A comprises: during a first operation stateof a first mode of the charge pump, performing steps of: disabling afirst flying capacitor; connecting a first terminal and a secondterminal of a second flying capacitor to a first output capacitor and aground terminal, respectively; and supplying the input voltage to thefirst terminal of the second flying capacitor to charge the secondflying capacitor and the first output capacitor, thereby generating thepositive voltage; during a second operation state of the first mode ofthe charge pump, performing steps of: disabling the first flyingcapacitor; and connecting the first and second terminals of the secondflying capacitor to the ground terminal and a second output capacitor,respectively, to make the second flying capacitor charge the secondoutput capacitor, thereby generating the negative voltage; during afirst operation state of a second mode of the charge pump, performingsteps of: connecting a second terminal of the first flying capacitor tothe first terminal of the second flying capacitor and the first outputcapacitor; connecting the second terminal of the second flying capacitorto the ground terminal; and supplying the input voltage to a firstterminal of the first flying capacitor to charge the first flyingcapacitor, the second flying capacitor and the first output capacitor,thereby generating the positive voltage; and during a second operationstate of the second mode of the charge pump, performing steps of:connecting the first terminal of the first flying capacitor to the firstoutput capacitor; connecting the second terminal of the first flyingcapacitor and the first terminal of the second flying capacitor to theground terminal; and connecting the second terminal of the second flyingcapacitor to the second output capacitor to charge the second outputcapacitor, thereby generating the negative voltage.
 28. The controlmethod of claim 27, wherein the step of disabling the first flyingcapacitor comprises making a short circuit between the first and secondterminals of the first flying capacitor or floating the first terminalof the first flying capacitor.
 29. The control method of claim 27,further comprising, during the first operation state of the first modeof the charge pump, detecting the positive voltage and stoppingsupplying the input voltage when the positive voltage becomes greaterthan a target value.
 30. The control method of claim 29, furthercomprising adjusting the target value to adjust the positive voltage orthe negative voltage.
 31. The control method of claim 27, furthercomprising, during the first operation state of the second mode of thecharge pump, detecting a voltage at the first terminal of the firstflying capacitor and stopping supplying the input voltage when thevoltage at the first terminal of the first flying capacitor becomesgreater than a target value.
 32. The control method of claim 31, furthercomprising adjusting the target value to adjust the positive voltage orthe negative voltage.
 33. The control method of claim 22, wherein thestep A comprises: during a first operation state of a first mode of thecharge pump, performing steps of: connecting a first terminal and asecond terminal of a first flying capacitor to a first output capacitorand a first terminals of a second flying capacitor, respectively;connecting a second terminal of the second flying capacitor to a groundterminal; and supplying the input voltage to the first terminal of thefirst flying capacitor to charge the first flying capacitor, the secondflying capacitor and the first output capacitor, thereby generating thepositive voltage; during a second operation state of the first mode ofthe charge pump, performing steps of: connecting the first and secondterminals of the first flying capacitor to the ground terminal and thesecond flying capacitor, respectively; and connecting the secondterminal of the second flying capacitor to a second output capacitor tocharge the second output capacitor, thereby generating the negativevoltage; during a first operation state of a second mode of the chargepump, performing steps of: connecting a second terminal of the firstflying capacitor to the first terminal of the second flying capacitorand the first output capacitor; connecting the second terminal of thesecond flying capacitor to the ground terminal; and supplying the inputvoltage to a first terminal of the first flying capacitor to charge thefirst flying capacitor, the second flying capacitor and the first outputcapacitor, thereby generating the positive voltage; and during a secondoperation state of the second mode of the charge pump, performing stepsof: connecting the first terminal of the first flying capacitor to thefirst output capacitor; connecting the second terminal of the firstflying capacitor and the first terminal of the second flying capacitorto the ground terminal; and connecting the second terminal of the secondflying capacitor to the second output capacitor to charge the secondoutput capacitor, thereby generating the negative voltage.
 34. Thecontrol method of claim 33, further comprising, during the firstoperation state of the first mode of the charge pump, detecting thepositive voltage and stopping supplying the input voltage when thepositive voltage becomes greater than a target value.
 35. The controlmethod of claim 34, further comprising adjusting the target value toadjust the positive voltage or the negative voltage.
 36. The controlmethod of claim 33, further comprising, during the first operation stateof the second mode of the charge pump, detecting a voltage at the firstterminal of the first flying capacitor and stopping supplying the inputvoltage when the voltage at the first terminal of the first flyingcapacitor becomes greater than a target value.
 37. The control method ofclaim 36, further comprising adjusting the target value to adjust thepositive voltage or the negative voltage.
 38. The control method ofclaim 22, wherein the step A comprises: during a first operation stateof a first mode of the charge pump, performing steps of: connecting afirst terminal and a second terminal of a first flying capacitor to afirst output capacitor and a ground terminal, respectively; disabling asecond flying capacitor whose second terminal is grounded; and supplyingthe input voltage to a first terminal of the first flying capacitor tocharge the first flying capacitor and the first output capacitor,thereby generating the positive voltage; during a second operation stateof the first mode of the charge pump, performing steps of: connectingthe first and second terminals of the first flying capacitor to theground terminal and a second output capacitor, respectively, to make thefirst flying capacitor charge the second output capacitor, therebygenerating the negative voltage; and disabling the second flyingcapacitor; during a first operation state of a second mode of the chargepump, performing steps of: connecting the second terminal of the firstflying capacitor to the first terminal of the second flying capacitor;and supplying the input voltage to a first terminal of the first flyingcapacitor to charge the first flying capacitor and the second flyingcapacitor; during a second operation state of the second mode of thecharge pump, connecting the first and second terminals of the firstflying capacitor to the first output capacitor and the ground terminal,respectively and connecting the first terminal of the second flyingcapacitor to the first output capacitor, to make the first and secondflying capacitors charge the first output capacitor, thereby generatingthe positive voltage; and during a third operation state of the secondmode of the charge pump, performing steps of: connecting the first andsecond terminals of the first flying capacitor to the ground terminaland the second output capacitor, respectively, to make the first flyingcapacitor charge the second output capacitor, thereby generating thenegative voltage; and disabling the second flying capacitor.
 39. Thecontrol method of claim 38, wherein the step of disabling the secondflying capacitor comprises floating the first terminal of the secondflying capacitor.
 40. The control method of claim 38, furthercomprising, during the first operation state of the first mode of thecharge pump, detecting the positive voltage and stopping supplying theinput voltage when the positive voltage becomes greater than a targetvalue.
 41. The control method of claim 40, further comprising adjustingthe target value to adjust the positive voltage or the negative voltage.42. The control method of claim 38, further comprising, during the firstoperation state of the second mode of the charge pump, detecting avoltage at the first terminal of the first flying capacitor and stoppingsupplying the input voltage when the voltage at the first terminal ofthe first flying capacitor becomes greater than a target value.
 43. Thecontrol method of claim 42, further comprising adjusting the targetvalue to adjust the positive voltage or the negative voltage.
 44. Acharge pump comprising: a first bonding pad and a second bonding pad fora first flying capacitor connected therebetween; a third bonding pad andthe second bonding pad for a second flying capacitor connectedtherebetween; an input terminal receiving an input voltage; a firstoutput terminal connected to a first output capacitor, providing apositive voltage; a second output terminal connected to a second outputcapacitor, providing a negative voltage; a first switch connectedbetween the input terminal and the first bonding pad; a second switchconnected between the second bonding pad and a ground terminal; a thirdswitch connected between the third bonding pad and the ground terminal;a fourth switch connected between the first bonding pad and the firstoutput terminal; a fifth switch connected between the second bonding padand the first output terminal; a sixth switch connected between thethird bonding pad and the second output terminal; and a clock generatorconnected to the first through sixth switches, operative to generatefirst through sixth signals to control the first through sixth switches,respectively.
 45. The charge pump of claim 44, further comprising: adetector connected to the first bonding pad, detecting a first voltageof the first bonding pad to generate a second voltage related to thefirst voltage; a reference voltage generator providing a variablereference voltage for controlling the positive voltage or the negativevoltage; and a comparator connected to the detector and the referencevoltage generator, comparing the second voltage with the referencevoltage to turn off the first switch when the second voltage becomesgreater than the reference voltage.
 46. The charge pump of claim 45,wherein during a first operation state of a first mode of the chargepump, the first, third, fourth and fifth switches are turned on and thesecond and sixth switches are turned off; during a second operationstate of the first mode of the charge pump, the first, third, fourth andfifth switches are turned off and the second and sixth switches areturned on; during a first operation state of a second mode of the chargepump, the first, third and fifth switches are turned on and the second,fourth and sixth switches are turn off; during a second operation stateof the second mode of the charge pump, the first, third and fifthswitches are turned off and the second, fourth and sixth switches areturned on.
 47. The charge pump of claim 45, further comprising a seventhswitch connected between the first bonding pad and the ground terminal,controlled by a seventh signal provided by the clock generator.
 48. Thecharge pump of claim 47, wherein during a first operation state of afirst mode of the charge pump, the first, third and fourth switches areturned on and the second, fifth, sixth and seventh switches are turnedoff; during a second operation state of the first mode of the chargepump, the first, second, third, fourth and fifth switches are turned offand the sixth and seventh switches are turned on; during a firstoperation state of a second mode of the charge pump, the first, thirdand fifth switches are turned on and the second, fourth, sixth andseventh switches are turned off; and during a second operation state ofthe second mode of the charge pump, the first, third, fifth and seventhswitches are turned off and the second, fourth and sixth switches areturn on.
 49. The charge pump of claim 44, wherein during a firstoperation state of a first mode of the charge pump, the first, third,fourth and fifth switches are turned on and the second and sixthswitches are turned off; during a second operation state of the firstmode of the charge pump, the first, third, fourth and fifth switches areturned off and the second and sixth switches are turned on; during afirst operation state of a second mode of the charge pump, the first,third and fifth switches are turned on and the second, fourth and sixthswitches are turn off; during a second operation state of the secondmode of the charge pump, the first, third and fifth switches are turnedoff and the second, fourth and sixth switches are turned on.
 50. Thecharge pump of claim 44, further comprising a seventh switch connectedbetween the first bonding pad and the ground terminal, controlled by aseventh signal provided by the clock generator.
 51. The charge pump ofclaim 50, wherein during a first operation state of a first mode of thecharge pump, the first, third and fourth switches are turned on and thesecond, fifth, sixth and seventh switches are turned off; during asecond operation state of the first mode of the charge pump, the first,second, third, fourth and fifth switches are turned off and the sixthand seventh switches are turned on; during a first operation state of asecond mode of the charge pump, the first, third and fifth switches areturned on and the second, fourth, sixth and seventh switches are turnedoff; and during a second operation state of the second mode of thecharge pump, the first, third, fifth and seventh switches are turned offand the second, fourth and sixth switches are turn on.
 52. The chargepump of claim 44, wherein the charge pump further comprises a seventhswitch connected between the input terminal and the second bonding pad,controlled by a seventh signal determined by the clock signal and themode select signal by the clock generator.
 53. The charge pump of claim52, wherein the charge pump further comprises: a detector connected tothe first and second bonding pads, detecting a first voltage of thefirst bonding pad during a second mode of the charge pump to generate asecond voltage, and detecting a third voltage of the second bonding padduring a first mode of the charge pump to generate the second voltage; areference voltage generator providing a variable reference voltage forcontrolling the positive voltage or the negative voltage; and acomparator connected to the detector and the reference voltagegenerator, comparing the second voltage with the reference voltage toturn off the seventh switch during the first mode of the charge pumpwhen the second voltage becomes greater than the reference voltage, andto turn off the first switch during the second mode of the charge pumpwhen the second voltage becomes greater than the reference voltage. 54.The charge pump of claim 53, wherein during a first operation state ofthe first mode of the charge pump, the first, second, fourth and sixthswitches are turned off and the third, fifth and seventh switches areturned on; during a second operation state of the first mode of thecharge pump, the first, third, fourth, fifth and seventh switches areturned off and the second and sixth switches are turned on; during afirst operation state of the second mode of the charge pump, the first,third and fifth switches are turned on and the second, fourth, sixth andseventh switches are turned off; during a second operation state of thesecond mode of the charge pump, the first, third, fifth and seventhswitches are turned off and the second, fourth and sixth switches areturn on.
 55. The charge pump of claim 52, wherein during a firstoperation state of a first mode of the charge pump, the first, second,fourth and sixth switches are turned off and the third, fifth andseventh switches are turned on; during a second operation state of thefirst mode of the charge pump, the first, third, fourth, fifth andseventh switches are turned off and the second and sixth switches areturned on; during a first operation state of a second mode of the chargepump, the first, third and fifth switches are turned on and the second,fourth, sixth and seventh switches are turned off; and during a secondoperation state of the second mode of the charge pump, the first, third,fifth and seventh switches are turned off and the second, fourth andsixth switches are turn on.
 56. A charge pump comprising: a firstbonding pad and a second bonding pad for a first flying capacitorconnected therebetween; a third bonding pad connected to a second flyingcapacitor; an input terminal receiving an input voltage a first outputterminal connected to a first output capacitor, providing a positivevoltage; a second output terminal connected to a second outputcapacitor, providing a negative voltage; a first switch connectedbetween the input terminal and the first bonding pad; a second switchconnected between the second bonding pad and a ground terminal; a thirdswitch connected between the first bonding pad and the first outputterminal; a fourth switch connected between the first bonding pad andthe ground terminal; a fifth switch connected between the second bondingpad and the second output terminal; a sixth switch connected between thesecond bonding pad and the third bonding pad; a seventh switch connectedbetween the first bonding pad and the third bonding pad; and a clockgenerator connected to the first through seventh switches, operative togenerate first through seventh signals according to the clock signal andthe mode select signal to control the first through seventh switches,respectively.
 57. The charge pump of claim 56, further comprising: adetector connected to the first bonding pad, detecting a first voltageof the first bonding pad to generate a second voltage related to thefirst voltage; a reference voltage generator providing a variablereference voltage for controlling the positive voltage or the negativevoltage; and a comparator connected to the detector and the referencevoltage generator, comparing the second voltage with the referencevoltage to turn off the first switch when the second voltage becomesgreater than the reference voltage.
 58. The charge pump of claim 57,wherein during a first operation state of a first mode of the chargepump, the first through third switches are turned on and the fourththrough seventh switches are turned off; during a second operation stateof the first mode of the charge pump, the first, second, third, sixthand seventh switches are turned off and the fourth and fifth switchesare turned on; during a first operation state of a second mode of thecharge pump, the first and sixth switches are turned on and the second,third, fourth, fifth and seventh switches are turned off; during asecond operation state of the second mode of the charge pump, the first,fourth, fifth and sixth switches are turned off and the second, thirdand seventh switches are turned on; and during a third operation stateof the second mode of the charge pump, the first, second, third, sixthand seventh switches are turned off and the fourth and fifth switchesare turned on.
 59. The charge pump of claim 56, wherein during a firstoperation state of a first mode of the charge pump, the first throughthird switches are turned on and the fourth through seventh switches areturned off; during a second operation state of the first mode of thecharge pump, the first, second, third, sixth and seventh switches areturned off and the fourth and fifth switches are turned on; during afirst operation state of a second mode of the charge pump, the first andsixth switches are turned on and the second, third, fourth, fifth andseventh switches are turned off; during a second operation state of thesecond mode of the charge pump, the first, fourth, fifth and sixthswitches are turned off and the second, third and seventh switches areturned on; and during a third operation state of the second mode of thecharge pump, the first, second, third, sixth and seventh switches areturned off and the fourth and fifth switches are turned on.
 60. Acontrol method for a charge pump, comprising: during a first operationstate of a first mode of the charge pump, performing steps of: disablinga first flying capacitor; connecting a first terminal and a secondterminal of a second flying capacitor to a first output capacitor and aground terminal, respectively; and supplying an input voltage to thefirst terminal of the second flying capacitor to charge the secondflying capacitor and the first output capacitor, thereby generating apositive voltage; during a second operation state of the first mode ofthe charge pump, performing steps of: disabling the first flyingcapacitor; and connecting the first and second terminals of the secondflying capacitor to the ground terminal and a second output capacitor,respectively, to make the second flying capacitor charge the secondoutput capacitor, thereby generating a negative voltage; during a firstoperation state of a second mode of the charge pump, performing stepsof: connecting the second terminal of the first flying capacitor to thesecond flying capacitor and the first output capacitor; connecting thesecond terminal of the second flying capacitor to the ground terminal;and supplying the input voltage to a first terminal of the first flyingcapacitor to charge the first flying capacitor, the second flyingcapacitor and the first output capacitor, thereby generating thepositive voltage; and during a second operation state of the second modeof the charge pump, performing steps of: connecting the first terminalof the first flying capacitor to the first output capacitor; connectingthe second terminal of the first flying capacitor and the first terminalof the second flying capacitor to the ground terminal; and connectingthe second terminal of the second flying capacitor to the second outputcapacitor to charge the second output capacitor, thereby generating thenegative voltage.
 61. The control method of claim 60, wherein the stepof disabling the first flying capacitor comprises making a short circuitbetween the first and second terminals of the first flying capacitor orfloating the first terminal of the first flying capacitor.
 62. Thecontrol method of claim 60, further comprising, during the firstoperation state of the first mode of the charge pump, detecting thepositive voltage and stopping supplying the input voltage when thepositive voltage becomes greater than a target value.
 63. The controlmethod of claim 62, further comprising adjusting the target value toadjust the positive voltage or the negative voltage.
 64. The controlmethod of claim 60, further comprising, during the first operation stateof the second mode of the charge pump, detecting a voltage at the firstterminal of the first flying capacitor and stopping supplying the inputvoltage when the voltage at the first terminal of the first flyingcapacitor becomes greater than a target value.
 65. The control method ofclaim 64, further comprising adjusting the target value to adjust thepositive voltage or the negative voltage.
 66. A control method for acharge pump, comprising: during a first operation state of a first modeof the charge pump, performing steps of: connecting a first terminal anda second terminal of a first flying capacitor to a first outputcapacitor and a first terminal of a second flying capacitor,respectively; connecting a second terminal of the second flyingcapacitor to a ground terminal; and supplying an input voltage to thefirst terminal of the first flying capacitor to charge the first flyingcapacitor, the second flying capacitor and the first output capacitor,thereby generating a positive voltage; during a second operation stateof the first mode of the charge pump, performing steps of: connectingthe first and second terminals of the first flying capacitor to theground terminal and the first terminal of the second flying capacitor,respectively; and connecting the second terminal of the second flyingcapacitor to a second output capacitor to charge the second outputcapacitor, thereby generating a negative voltage; during a firstoperation state of a second mode of the charge pump, performing stepsof: connecting a second terminal of the first flying capacitor to thefirst terminal of the second flying capacitor and the first outputcapacitor; connecting the second terminal of the second flying capacitorto the ground terminal; and supplying the input voltage to a firstterminal of the first flying capacitor to charge the first flyingcapacitor, the second flying capacitor and the first output capacitor,thereby generating the positive voltage; and during a second operationstate of the second mode of the charge pump, performing steps of:connecting the first terminal of the first flying capacitor to the firstoutput capacitor; connecting the second terminal of the first flyingcapacitor and the first terminal of the second flying capacitor to theground terminal; and connecting the second terminal of the second flyingcapacitor to the second output capacitor to charge the second outputcapacitor, thereby generating the negative voltage.
 67. The controlmethod of claim 66, further comprising, during the first operation stateof the first mode of the charge pump, detecting the positive voltage andstopping supplying the input voltage when the positive voltage becomesgreater than a target value.
 68. The control method of claim 67, furthercomprising adjusting the target value to adjust the positive voltage orthe negative voltage.
 69. The control method of claim 66, furthercomprising, during the first operation state of the second mode of thecharge pump, detecting a voltage at the first terminal of the firstflying capacitor and stopping supplying the input voltage when thevoltage at the first terminal of the first flying capacitor becomesgreater than a target value.
 70. The control method of claim 69, furthercomprising adjusting the target value to adjust the positive voltage orthe negative voltage.
 71. A control method for a charge pump, comprisingsteps of: during a first operation state of a first mode of the chargepump, performing steps of: connecting a first terminal and a secondterminal of a first flying capacitor to a first output capacitor and aground terminal, respectively; disabling the second flying capacitorwhose second terminal is grounded; and supplying the input voltage to afirst terminal of the first flying capacitor to charge the first flyingcapacitor and the first output capacitor, thereby generating a positivevoltage; during a second operation state of the first mode of the chargepump, performing steps of: connecting the first and second terminals ofthe first flying capacitor to the ground terminal and a second outputcapacitor, respectively, to make the first flying capacitor charge thesecond output capacitor, thereby generating a negative voltage; anddisabling the second flying capacitor; during a first operation state ofa second mode of the charge pump, performing steps of: connecting thesecond terminal of the first flying capacitor to a first terminal of thesecond flying capacitor; and supplying the input voltage to a firstterminal of the first flying capacitor to charge the first flyingcapacitor and the second flying capacitor; during a second operationstate of the second mode of the charge pump, connecting the first andsecond terminals of the first flying capacitor to the first outputcapacitor and the ground terminal, respectively and connecting the firstterminal of the second flying capacitor to the first output capacitor,to make the first flying capacitor and the second flying capacitorcharge the first output capacitor, thereby generating the positivevoltage; and during a third operation state of the second mode of thecharge pump, performing steps of: connecting the first and secondterminals of the first flying capacitor to the ground terminal and thesecond output capacitor, respectively, to make the first flyingcapacitor charge the second output capacitor, thereby generating thenegative voltage; and disabling the second flying capacitor.
 72. Thecontrol method of claim 54, wherein the step of disabling the secondflying capacitor comprises floating the first terminal of the secondflying capacitor.
 73. The control method of claim 54, furthercomprising, during the first operation state of the first mode of thecharge pump, detecting the positive voltage and stopping supplying theinput voltage when the positive voltage becomes greater than a targetvalue.
 74. The control method of claim 73, further comprising adjustingthe target value to adjust the positive voltage or the negative voltage.75. The control method of claim 54, further comprising, during the firstoperation state of the second mode of the charge pump, detecting avoltage at the first terminal of the first flying capacitor and stoppingsupplying the input voltage when the voltage at the first terminal ofthe first flying capacitor becomes greater than a target value.
 76. Thecontrol method of claim 75, further comprising adjusting the targetvalue to adjust the positive voltage or the negative voltage.
 77. Acontrol circuit for an audio amplifier including a power stage togenerate an output signal according to a signal at an input terminalthereof for driving one or more speakers, and a gain setting circuit toprovide a setting signal to control a gain of the power stage, thecontrol circuit comprising: a charge pump connected to the power stage,operative to convert an input voltage into a variable positive voltageand a variable negative voltage for supplying to the power stage togenerate the output signal; an adaptive voltage controller connected tothe charge pump, operative to detect a level of a signal related to theoutput signal to generate a mode select signal for the charge pump,thereby determining an operation mode of the charge pump; and aswitching frequency controller connected to the charge pump, operativeto generate a clock signal according to the setting signal for thecharge pump, thereby determining a switching frequency of the chargepump.
 78. The control circuit of claim 77, wherein the adaptive voltagecontroller detects a level of the output signal to generate the modeselect signal.
 79. The control circuit of claim 77, wherein the adaptivevoltage controller detects a level of a signal at an input terminal ofthe power stage to generate the mode select signal.
 80. The controlcircuit of claim 77, further comprising an amplitude level settingcircuit connected to the adaptive voltage controller, operative toprovide a plurality of reference voltages to the adaptive voltagecontroller, wherein the plurality of reference voltages are comparedwith the signal related to the output signal to identify the level ofthe signal related to the output signal.
 81. The control circuit ofclaim 77, wherein the adaptive voltage controller comprises adesign-for-test circuit operative to test the output signal foridentifying whether a magnitude of the output signal is correct.
 82. Thecontrol circuit of claim 77, wherein the charge pump comprises: a firstbonding pad and a second bonding pad for a first flying capacitorconnected therebetween; a third bonding pad and the second bonding padfor a second flying capacitor connected therebetween; an input terminalreceiving the input voltage; a first output terminal connected to afirst output capacitor, providing the positive voltage; a second outputterminal connected to a second output capacitor, providing the negativevoltage; a first switch connected between the input terminal and thefirst bonding pad; a second switch connected between the second bondingpad and a ground terminal; a third switch connected between the thirdbonding pad and the ground terminal; a fourth switch connected betweenthe first bonding pad and the first output terminal; a fifth switchconnected between the second bonding pad and the first output terminal;a sixth switch connected between the third bonding pad and the secondoutput terminal; and a clock generator connected to the adaptive voltagecontroller, the switching frequency controller and the first throughsixth switches, operative to generate first through sixth signalsaccording to the clock signal and the mode select signal to control thefirst through sixth switches, respectively.
 83. The control circuit ofclaim 82, wherein the charge pump further comprises: a detectorconnected to the first bonding pad, detecting a first voltage of thefirst bonding pad to generate a second voltage related to the firstvoltage; a reference voltage generator providing a variable referencevoltage for controlling the positive voltage or the negative voltage;and a comparator connected to the detector and the reference voltagegenerator, comparing the second voltage with the reference voltage toturn off the first switch when the second voltage becomes greater thanthe reference voltage.
 84. The control circuit of claim 83, whereinduring a first operation state of a first mode of the charge pump, thefirst, third, fourth and fifth switches are turned on and the second andsixth switches are turned off; during a second operation state of thefirst mode of the charge pump, the first, third, fourth and fifthswitches are turned off and the second and sixth switches are turned on;during a first operation state of a second mode of the charge pump, thefirst, third and fifth switches are turned on and the second, fourth andsixth switches are turn off; and during a second operation state of thesecond mode of the charge pump, the first, third and fifth switches areturned off and the second, fourth and sixth switches are turned on. 85.The control circuit of claim 83, wherein the charge pump furthercomprises a seventh switch connected between the first bonding pad andthe ground terminal, controlled by a seventh signal determined by theclock signal and the mode select signal by the clock generator.
 86. Thecontrol circuit of claim 85, wherein during a first operation state of afirst mode of the charge pump, the first, third and fourth switches areturned on and the second, fifth, sixth and seventh switches are turnedoff; during a second operation state of the first mode of the chargepump, the first through fifth switches are turned off and the sixth andseventh switches are turned on; during a first operation state of asecond mode of the charge pump, the first, third and fifth switches areturned on and the second, fourth, sixth and seventh switches are turnedoff; and during a second operation state of the second mode of thecharge pump, the first, third, fifth and seventh switches are turned offand the second, fourth and sixth switches are turn on.
 87. The controlcircuit of claim 82, wherein during a first operation state of a firstmode of the charge pump, the first, third, fourth and fifth switches areturned on and the second and sixth switches are turned off; during asecond operation state of the first mode of the charge pump, the first,third, fourth and fifth switches are turned off and the second and sixthswitches are turned on; during a first operation state of a second modeof the charge pump, the first, third and fifth switches are turned onand the second, fourth and sixth switches are turn off; and during asecond operation state of the second mode of the charge pump, the first,third and fifth switches are turned off and the second, fourth and sixthswitches are turned on.
 88. The control circuit of claim 82, wherein thecharge pump further comprises a seventh switch connected between thefirst bonding pad and the ground terminal, controlled by a seventhsignal determined by the clock signal and the mode select signal by theclock generator.
 89. The control circuit of claim 88, wherein during afirst operation state of a first mode of the charge pump, the first,third and fourth switches are turned on and the second, fifth, sixth andseventh switches are turned off; during a second operation state of thefirst mode of the charge pump, the first through fifth switches areturned off and the sixth and seventh switches are turned on; during afirst operation state of a second mode of the charge pump, the first,third and fifth switches are turned on and the second, fourth, sixth andseventh switches are turned off; and during a second operation state ofthe second mode of the charge pump, the first, third, fifth and seventhswitches are turned off and the second, fourth and sixth switches areturn on.
 90. The control circuit of claim 82, wherein the charge pumpfurther comprises a seventh switch connected between the input terminaland the second bonding pad, controlled by a seventh signal determined bythe clock signal and the mode select signal by the clock generator. 91.The control circuit of claim 90, wherein the charge pump furthercomprises: a detector connected to the first and second bonding pads,detecting a first voltage of the first bonding pad during a second modeof the charge pump to generate a second voltage, and detecting a thirdvoltage of the second bonding pad during a first mode of the charge pumpto generate the second voltage; a reference voltage generator providinga variable reference voltage for controlling the positive voltage or thenegative voltage; and a comparator connected to the detector and thereference voltage generator, comparing the second voltage with thereference voltage to turn off the seventh switch during the first modeof the charge pump when the second voltage becomes greater than thereference voltage, and to turn off the first switch during the secondmode of the charge pump when the second voltage becomes greater than thereference voltage.
 93. The control circuit of claim 90, wherein during afirst operation state of the first mode of the charge pump, the first,second, fourth and sixth switches are turned off and the third, fifthand seventh switches are turned on; during a second operation state ofthe first mode of the charge pump, the first, third, fourth, fifth andseventh switches are turned off and the second and sixth switches areturned on; during a first operation state of the second mode of thecharge pump, the first, third and fifth switches are turned on and thesecond, fourth, sixth and seventh switches are turned off; and during asecond operation state of the second mode of the charge pump, the first,third, fifth, seventh switches are turned off and the second, fourth andsixth switches are turned on.
 92. The control circuit of claim 91,wherein during a first operation state of a first mode of the chargepump, the first, second, fourth and sixth switches are turned off andthe third, fifth and seventh switches are turned on; during a secondoperation state of the first mode of the charge pump, the first, third,fourth, fifth and seventh switches are turned off and the second andsixth switches are turned on; during a first operation state of a secondmode of the charge pump, the first, third and fifth switches are turnedon and the second, fourth, sixth and seventh switches are turned off;and during a second operation state of the second mode of the chargepump, the first, third, fifth, seventh switches are turned off and thesecond, fourth and sixth switches are turned on.
 94. The control circuitof claim 77, wherein the charge pump comprises: a first bonding pad anda second bonding pad for a first flying capacitor connectedtherebetween; a third bonding pad connected to a second flyingcapacitor; an input terminal receiving the input voltage a first outputterminal connected to a first output capacitor, providing the positivevoltage; a second output terminal connected to a second outputcapacitor, providing the negative voltage; a first switch connectedbetween the input terminal and the first bonding pad; a second switchconnected between the second bonding pad and a ground terminal; a thirdswitch connected between the first bonding pad and the first outputterminal; a fourth switch connected between the first bonding pad andthe ground terminal; a fifth switch connected between the second bondingpad and the second output terminal; a sixth switch connected between thesecond bonding pad and the third bonding pad; a seventh switch connectedbetween the first bonding pad and the third bonding pad; and a clockgenerator connected to the adaptive voltage controller, the switchingfrequency controller and the first through seventh switches, operativeto generate first through seventh signals according to the clock signaland the mode select signal to control the first through seventhswitches, respectively.
 95. The control circuit of claim 94, wherein thecharge pump further comprises: a detector connected to the first bondingpad, detecting a first voltage of the first bonding pad to generate asecond voltage related to the first voltage; a reference voltagegenerator providing a variable reference voltage for controlling thepositive voltage or the negative voltage; and a comparator connected tothe detector and the reference voltage generator, comparing the secondvoltage with the reference voltage to turn off the first switch when thesecond voltage becomes greater than the reference voltage.
 96. Thecontrol circuit of claim 95, wherein during a first operation state of afirst mode of the charge pump, the first through third switches areturned on and the fourth through seventh switches are turned off; duringa second operation state of the first mode of the charge pump, thefirst, second, third, sixth and seventh switches are turned off and thefourth and fifth switches are turned on; during a first operation stateof a second mode of the charge pump, the first and sixth switches areturned on and the second, third, fourth, fifth and seventh switches areturned off; during a second operation state of the second mode of thecharge pump, the first, fourth, fifth and sixth switches are turned offand the second, third and seventh switches are turned on; and during athird operation state of the second mode of the charge pump, the firstthrough third switches, and the sixth and seventh switches are turnedoff and the fourth and fifth switches are turned on.
 97. The controlcircuit of claim 94, wherein during a first operation state of a firstmode of the charge pump, the first through third switches are turned onand the fourth through seventh switches are turned off; during a secondoperation state of the first mode of the charge pump, the first, second,third, sixth and seventh switches are turned off and the fourth andfifth switches are turned on; during a first operation state of a secondmode of the charge pump, the first and sixth switches are turned on andthe second, third, fourth, fifth and seventh switches are turned off;during a second operation state of the second mode of the charge pump,the first, fourth, fifth and sixth switches are turned off and thesecond, third and seventh switches are turned on; and during a thirdoperation state of the second mode of the charge pump, the first,second, third, sixth and seventh switches are turned off and the fourthand fifth switches are turned on.
 98. A control method for an audioamplifier including a power stage to generate an output signal accordingto a signal at an input terminal thereof for driving one or morespeakers, and a gain setting circuit to provide a setting signal tocontrol a gain of the power stage, the control method comprising: A.)converting an input voltage into a variable positive voltage and avariable negative voltage by a charge pump for supplying to the powerstage to generate the output signal; B.) detecting a level of a signalrelated to the output signal for generating a mode select signal todetermine an operation mode of the charge pump; and C.) generating aclock signal according to the setting signal to determine a switchingfrequency of the charge pump.
 99. The control method of claim 98,wherein the step B comprises detecting a level of the output signal togenerate the mode select signal.
 100. The control method of claim 98,wherein the step B comprises detecting a level of the signal at theinput terminal of the power stage to generate the mode select signal.101. The control method of claim 98, wherein the step B comprisesproviding a plurality of reference voltages to be compared with thesignal related to the output signal to identify the level of the signalrelated to the output signal.
 102. The control method of claim 98,further comprising testing the output signal to identify whether amagnitude of the output signal is correct.
 103. The control method ofclaim 98, wherein the step A comprises: during a first operation stateof a first mode of the charge pump, performing steps of: disabling afirst flying capacitor; connecting a first terminal and a secondterminal of a second flying capacitor to a first output capacitor and aground terminal, respectively; and supplying the input voltage to thefirst terminal of the second flying capacitor to charge the secondflying capacitor and the first output capacitor, thereby generating thepositive voltage; during a second operation state of the first mode ofthe charge pump, performing steps of: disabling the first flyingcapacitor; and connecting the first and second terminals of the secondflying capacitor to the ground terminal and a second output capacitor,respectively, to make the second flying capacitor charge the secondoutput capacitor, thereby generating the negative voltage; during afirst operation state of a second mode of the charge pump, performingsteps of: connecting a second terminal of the first flying capacitor tothe first terminal of the second flying capacitor and the first outputcapacitor; connecting the second terminal of the second flying capacitorto the ground terminal; and supplying the input voltage to a firstterminal of the first flying capacitor to charge the first flyingcapacitor, the second flying capacitor and the first output capacitor,thereby generating the positive voltage; and during a second operationstate of the second mode of the charge pump, performing steps of:connecting the first terminal of the first flying capacitor to the firstoutput capacitor; connecting the second terminal of the first flyingcapacitor and the first terminal of the second flying capacitor to theground terminal; and connecting the second terminal of the second flyingcapacitor to the second output capacitor to charge the second outputcapacitor, thereby generating the negative voltage.
 104. The controlmethod of claim 103, wherein the step of disabling the first flyingcapacitor comprises making a short circuit between the first and secondterminals of the first flying capacitor or floating the first terminalof the first flying capacitor.
 105. The control method of claim 103,further comprising, during the first operation state of the first modeof the charge pump, detecting the positive voltage and stoppingsupplying the input voltage when the positive voltage becomes greaterthan a target value.
 106. The control method of claim 105, furthercomprising adjusting the target value to adjust the positive voltage orthe negative voltage.
 107. The control method of claim 103, furthercomprising, during the first operation state of the second mode of thecharge pump, detecting a voltage at the first terminal of the firstflying capacitor and stopping supplying the input voltage when thevoltage at the first terminal of the first flying capacitor becomesgreater than a target value.
 108. The control method of claim 107,further comprising adjusting the target value to adjust the positivevoltage or the negative voltage.
 109. The control method of claim 98,wherein the step A comprises: during a first operation state of a firstmode of the charge pump, performing steps of: connecting a firstterminal and a second terminal of a first flying capacitor to a firstoutput capacitor and a first terminal of a second flying capacitor,respectively; connecting a second terminal of the second flyingcapacitor to a ground terminal; and supplying the input voltage to afirst terminal of the first flying capacitor to charge the first flyingcapacitor, the second flying capacitor and the first output capacitor,thereby generating the positive voltage; during a second operation stateof the first mode of the charge pump, performing steps of: connectingthe first and second terminals of the first flying capacitor to theground terminal and the second flying capacitor, respectively; andconnecting the second terminal of the second flying capacitor to asecond output capacitor to charge the second output capacitor, therebygenerating the negative voltage; during a first operation state of asecond mode of the charge pump, performing steps of: connecting a secondterminal of the first flying capacitor to the first terminal of thesecond flying capacitor and the first output capacitor; connecting thesecond terminal of the second flying capacitor to the ground terminal;and supplying the input voltage to a first terminal of the first flyingcapacitor to charge the first flying capacitor, the second flyingcapacitor and the first output capacitor, thereby generating thepositive voltage; and during a second operation state of the second modeof the charge pump, performing steps of: connecting the first terminalof the first flying capacitor to the first output capacitor; connectingthe second terminal of the first flying capacitor and the first terminalof the second flying capacitor to the ground terminal; and connectingthe second terminal of the second flying capacitor to the second outputcapacitor to charge the second output capacitor, thereby generating thenegative voltage.
 110. The control method of claim 109, furthercomprising, during the first operation state of the first mode of thecharge pump, detecting the positive voltage and stopping supplying theinput voltage when the positive voltage becomes greater than a targetvalue.
 111. The control method of claim 110, further comprisingadjusting the target value to adjust the positive voltage or thenegative voltage.
 112. The control method of claim 110, furthercomprising, during the first operation state of the second mode of thecharge pump, detecting a voltage at the first terminal of the firstflying capacitor and stopping supplying the input voltage when thevoltage at the first terminal of the first flying capacitor becomesgreater than a target value.
 113. The control method of claim 112,further comprising adjusting the target value to adjust the positivevoltage or the negative voltage.
 114. The control method of claim 98,wherein the step A comprises: during a first operation state of a firstmode of the charge pump, performing steps of: connecting a firstterminal and a second terminal of a first flying capacitor to a firstoutput capacitor and a ground terminal, respectively; disabling thesecond flying capacitor whose second terminal is grounded; and supplyingthe input voltage to a first terminal of the first flying capacitor tocharge the first flying capacitor and the first output capacitor,thereby generating the positive voltage; during a second operation stateof the first mode of the charge pump, performing steps of: connectingthe first and second terminals of the first flying capacitor to theground terminal and a second output capacitor, respectively, to make thefirst flying capacitor charge the second output capacitor, therebygenerating the negative voltage; and disabling the second flyingcapacitor; during a first operation state of a second mode of the chargepump, performing steps of: connecting the second terminal of the firstflying capacitor to the first terminal of the second flying capacitor;and supplying the input voltage to a first terminal of the first flyingcapacitor to charge the first flying capacitor and the second flyingcapacitor; during a second operation state of the second mode of thecharge pump, connecting the first and second terminals of the firstflying capacitor to the first output capacitor and the ground terminal,respectively and connecting the first terminal of the second flyingcapacitor to the first output capacitor, to make the first and secondflying capacitors charge the first output capacitor, thereby generatingthe positive voltage; and during a third operation state of the secondmode of the charge pump, performing steps of: connecting the first andsecond terminals of the first flying capacitor to the ground terminaland the second output capacitor, respectively, to make the first flyingcapacitor charge the second output capacitor, thereby generating thenegative voltage; and disabling the second flying capacitor.
 115. Thecontrol method of claim 114, wherein the step of disabling the secondflying capacitor comprises floating the first terminal of the secondflying capacitor.
 116. The control method of claim 114, furthercomprising, during the first operation state of the first mode of thecharge pump, detecting the positive voltage and stopping supplying theinput voltage when the positive voltage becomes greater than a targetvalue.
 117. The control method of claim 116, further comprisingadjusting the target value to adjust the positive voltage or thenegative voltage.
 118. The control method of claim 114, furthercomprising, during the first operation state of the second mode of thecharge pump, detecting a voltage at the first terminal of the firstflying capacitor and stopping supplying the input voltage when thevoltage at the first terminal of the first flying capacitor becomesgreater than a target value.
 119. The control method of claim 118,further comprising adjusting the target value to adjust the positivevoltage or the negative voltage.